Restenosis due to intimal hyperplasia and vasoconstriction remains a major problem in treatments of arterial occlusive disease. Smooth muscle cells play a major role in vascular remodeling, and local control of their cellular phenotype would greatly enhance efforts to reduce the occurrence of restenosis. A common result of vascular injury is excessive remodeling of the extracellular matrix, which becomes rich in collagens and proteoglycans. While this leads to changes in biochemical properties, it also significantly alters biomechanical properties. Based on recent work that cells respond to substrata with varying mechanical properties, our central hypothesis is that the biomechanical properties of the substratum will modulate vascular smooth muscle cell cellular phenotype that is relevant for restenosis. Current therapies for restenosis largely involve soluble factors, but little attention has been focused on understanding the effects of substratum biomechanical properties on cellular phenotype. The objective of the proposed research is to create model systems that will recapitulate the biomechanical environment during vascular remodeling and to identify key relationships between substrate compliance and cellular phenotype associated with restenosis. This objective will be achieved by investigating the effect of substrate compliance on the cellular phenotype of smooth muscle cells on model bioengineered substrata that are designed to exhibit a systematic variation in their compliance ranging from the microscopic to macroscopic length scales. The outcome of this research will be a novel in vitro model system that will more closely mimic the biomechanical environment of the remodeled matrix in which one can test the effects of agents on vascular smooth muscle cell phenotype. This model system can also be applied to other pathophysiologic systems. Synthetic hydrogels will be used as model substrata in order to control the local mechanical compliance. Aim 1 is to develop bioengineered substrata with well-defined mechanical compliance at the macro- and microscales. Results from studies in Aims 2 and 3 will be used in the refinement of Aim 1. Aim 2 will establish and quantify relationships between substrate compliance and vascular smooth muscle cell phenotypes associated with restenosis. Aim 3 will test the effects of substrate compliance on the expression, localization, and activity of putative mechanosensing cellular components (integrins, cytoskeleton, FAK, paxillin, Rho GTPases). These studies will advance new insights on the physical factors that control phenotypic modulation of vascular smooth muscle cells with the aim of developing therapies to block restenosis.